Navegando por Assunto "Armadura para concreto armado"

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Acesso aberto (Open Access)
Análise experimental de lajes nervuradas de concreto armado com viga faixa de altura variável
(Universidade Federal do Pará, 2014-11-21) SACRAMENTO, Paulo Victor Prazeres; OLIVEIRA, Dênio Ramam Carvalho de; http://lattes.cnpq.br/1324105476558186
The ribbed slabs have been widely used in the buildings it has several advantages in its execution and performance. In order to get a good design of this type of slab is necessary ensure that the stresses are properly supported, mainly those considered critical, which can lead the structure to the collapse suddenly, as is the case of punching in connection wide beam-column or of the shear in the region of the ribbed. In order to evaluate the punching strength of the slab-column connection and the shear strength of the ribs were manufactured four reinforced concrete ribbed slabs, two slabs one-way and two slabs two-way. The flexural reinforcement rate was constant in all slabs. All slabs were square of side 2200 mm and thickness equal to 150 mm. The main variable in this study was the change in height of the wide beam. This variation has to evaluate the performance of the ribs, even when the limit of spacing between them is ensured. Also, check if the punching is a possibility of rupture in this case. The estimates in this step design were based on three different standards. These were ACI 318 (2008), Eurocode 2 (2004) and NBR 6118 (ABNT, 2014). Studies with ribbed slabs have shown that the estimates of design standards are conservative. In addition, this predictions may lead to inadequate results for resistance slabs. The experimental results of this series of tests were compared to the standard recommendations in order to assess the accuracy of these three standards, which refer to the ribbed slabs. Were also built computational models in order to verify that the behavior of slabs as the stress distribution both in connection wide beam-column range as the beam connection wide beam-ribbed. The results showed that the slabs connection wide beam-ribs must be treated in a careful manner due to the difference in stiffness between the solid area and the ribs.
Acesso aberto (Open Access)
Resistência à tração de conectores de aço embutidos em elementos de concreto armado
(Universidade Federal do Pará, 2016-03-04) COSTA, Hamilton Damasceno; FERREIRA, Maurício de Pina; http://lattes.cnpq.br/4242041552985485
In construction there are several situations where there is the need to transfer concentrated loads between elements of composite structures of steel and concrete, where it is common to use steel connectors. When connectors are required to tensile loads, the tensile strength can be considered a critical project. In this work were made two series of pull-out tests of anchors installed on reinforced concrete beams, a total of 16 trials. The first series of tests evaluated the influence of concrete cracking level on the pull-out strength of connectors, where the variables were effective embedment depth of connector (hef) with 60 mm and 110 mm, and the flexural reinforcement ratio of specimens (rf) ranging from 0,33% to 3,21%, the latter being the parameter which controlled the cracking level of the concrete specimens. The second series of tests evaluated the influence of the anchor reinforcement on the pull-out strength, where the variables were the diameter and spacing of the anchor reinforcement. The hef and rf remained constant values of 110 mm and 0,51%, respectively. Were also analyzed some theoretical models that predict the connector pull-out strength with and without anchor reinforcement. In the 1st series of tests, it was found that the level of cracking concrete, it has considerable influence on the pull-out strength of steel connectors, where the loss of pull-out strength is proportional to the cracking level of concrete. In the 2nd series of tests, it was observed that, connectors with anchor reinforcement, showed a gain of up to 320% on the load capacity of the connector. In the analysis of theoretical models that predict the tensile strength of connectors installed in uncracked concrete, the ACI 318 (2014), FIB BULLETIN 58 (2011) e EOTA/ETAG 001 (2010), showed better performances. For connectors with anchor reinforcement, the INFASO (2012) obtained better results with more accurate values and considerably less dispersed.